1. Field of the Invention
The present invention relates to an in-plane liquid crystal display (LCD) having electrodes with a curvature. More particularly, the present invention relates to an in-plane LCD capable of compensating a viewing angle in all directions by disposing a plurality of pixel electrodes and common electrodes, which generate an in-plane electric field, in a circular form, and capable of enhancing light efficiency by forming a compensation electrode at a region where disclination may occur as pixel electrodes and common electrodes cross an electrode connection line formed for electrical connection therebetween at an angle smaller than a right angle.
2. Description of the Related Art
With the development of the information society, various demands for display devices are increasing, and research for flat panel display such as an LCD (Liquid Crystal Display), PDP (Plasma Display Panel), an ELD (Electro Luminescent Display), an FED (Field Emission Display), a VFD (Vacuum Fluorescent Display) is actively ongoing. Of these displays, the LCD is most spotlighted because of its implementation of high picture quality, mass-production techniques, easiness of a driving unit, light weight, thinness, and low power consumption.
A LCD is divided into a liquid crystal panel for displaying images and a driving unit for applying a drive signal to the liquid crystal panel. The liquid crystal panel is divided into first and second substrates and a liquid crystal layer inserted between the first and second substrates.
The LCD has various display modes based upon an arrangement of fine, long liquid crystal molecules. Among the display modes, a TN (Twisted Nematic) mode LCD is advantageous in that it can easily display black and white and has a quick response speed and low driving voltage. However, in the TN mode, liquid crystal molecules are vertically aligned due to a vertically applied electric field. Hence, viewing angle characteristics are not good due to the refraction index anisotropy of the liquid crystal molecules. Thus, in order to overcome the shortcomings of the TN mode, a new technique, namely, an in-plane LCD, has been proposed.
The in-plane LCD is constructed such that when a voltage is applied, a horizontal electric field (in-plane) is formed on a plane to align the liquid crystal molecules on the plane to obtain wider viewing angle characteristics compared with the existing TN mode LCD.
FIG. 1 is a plan view of a unit pixel of an in-plane LCD in accordance with the related art, and FIG. 2 is a sectional view taken along line A-A′ of FIG. 1.
As shown in FIGS. 1 and 2, the in-plane LCD includes a data line 100 and a gate line 101 arranged on a first substrate 103 and defining a pixel region, a thin film transistor (TFT) (T) disposed at a crossing of the gate line 101 and the data line 100, and a pixel electrode 119 and a common electrode 111 formed approximately parallel to the data line 100.
The TFT (T) includes a gate electrode 110 formed on the first substrate 103 and connected with the gate line 101, a gate insulation film 113 staked on the gate electrode 110, a semiconductor layer 115 formed on the gate insulation film 113, an ohmic contact layer 116 formed on the semiconductor layer 115, and a source electrode 117 and a drain electrode 118 formed on the ohmic contact layer 116 and connected with the data line 100 and the pixel electrode 119, respectively.
The common electrode 111 is formed on the first substrate and connected with a common line 105, and the pixel electrode 119 is formed on the gate insulation film 113 and connected with the drain electrode 118 of the TFT (T).
A passivation film 120 is stacked over the entire surface of the substrate including the TFT, the pixel electrode 119 and the gate insulation film 113, on which a first alignment film (not shown) is coated and an alignment direction of the liquid crystal layer is determined. The liquid crystal molecules 102 are aligned in a rubbing direction between the common electrode 111 and the pixel electrode 119 when no voltage is applied thereto.
A light blocking layer 106 for preventing leakage of light, a color filter layer 107 consisting of R, G and B color filters, and an overcoat layer 108 are sequentially stacked on the second substrate 104 which corresponds to the first substrate 103.
The in-plane switching (IPS) LCD can be viewed at the front side in about a 70° direction up/down and leftward/rightward, obtaining a wide viewing angle compared with the existing TN mode. And, because the main viewing angle directions at different two domains formed by zigzag type electrodes are symmetrical, color shift is mutually compensated, not causing the color shift.
However, the IPS LCD has a limitation in improving the viewing angle characteristics. In other words, compared with the TN mode LCD, the two domain IPS LCD has better viewing angle characteristics and color shift characteristics. But when compared with the existing CRT, the viewing angle and color shift characteristics of the IPS LCD are still problematic.